The study is being directed by Geoffrey J. Gorse, M.D., professor of internal medicine in the division of infectious diseases and immunology. Gorse also is a staff physician at the Department of Veterans Affairs Medical Center in St. Louis.

The one-year study will involve approximately 4,000 veteran volunteers enrolled at 20 Veterans Affairs Medical Centers across the United States and Puerto Rico. Approximately 200 volunteers will be enrolled at each of the 20 participating sites. Each veteran aged 50 years and older with underlying chronic obstructive pulmonary disease and emphysema will be given the standard flu shot. Compared with healthy adults and children, patients with chronic obstructive pulmonary disease and emphysema are at particularly high risk for more severe influenza virus-caused illnesses and their related complications, including hospitalization and mortality.

Half of the enrolled volunteers will receive the investigational intranasal influenza vaccine, FluMist, and the other half will receive a nasal spray placebo in a randomized, double-blind, controlled clinical trial.

After vaccination, volunteers will be monitored for safety and immune responses to the vaccines. During the following winter influenza virus season, volunteers will be monitored for laboratory-documented influenza virus infection and influenza-like illness. Inoculations with the vaccines were completed last month.

Phase three trials are designed to study the safety and effectiveness of an experimental vaccine. These trials are a critical step in the clinical testing process that is needed for Food and Drug Administration (FDA) approval to license and market the product for specific clinical indications.

The investigational intranasal influenza vaccine being tested was developed by Aviron of Mountain View, Calif., and consists of three live, attenuated strains of influenza virus that are administered through a nasal spray, rather than by injection with a needle. The nasal spray vaccine has been tested in more than 5,500 volunteers in other trials, including children and healthy young adults.

In a randomized, placebo-controlled study recently reported by a team of Saint Louis University, Aviron and National Institute of Allergy and Infectious Diseases of National Institutes of Health supported researchers, 1 percent (14 of 1,070) of vaccinated children experienced culture-confirmed influenza, while 18 percent (95 of 532) of the placebo recipients experienced culture-confirmed influenza. The vaccine provided a 93 percent protection rate against influenza in healthy children.